Connection of protein transport and organelle contact sites in mitochondria
Ellenrieder L, Rampelt H, Becker T.
Mitochondria form contact sites to various cellular membranes including the endoplasmatic reticulum. The outer membrane of mitochondria is equipped with dedicated protein machineries that form such organelle contact sites. The best-studied mitochondrial contact site is formed by the ER-mitochondrial encounter structure (ERMES) in baker´s yeast Saccharomyces cerevisiae. The ERMES complex has been linked to many cellular processing including lipid transfer, mitochondria division, maintenance of the mitochondrial morphology and mitophagy. Mitochondrial functions depends on the import of proteins that are synthesized as precursors on cytosolic ribosomes. The translocase of the outer mitochondrial membrane (TOM complex) forms the general entry gate for almost all mitochondrial proteins. Strikingly, the TOM complex is closely connected to ER-mitochondria contact sites. Several TOM subunits are parts of these contact sites. In addition, the core ERMES subunit Mdm10 also associates with the sorting and assembly machinery (SAM complex). The SAM-Mdm10 complex promotes the biogenesis of the TOM complex. Thus, organelle contact sites are coordinated with protein import, which could be an important mechanism to coordinate processes important for mitochondrial biogenesis.
